The known types of method and device usually involve the introduction of an extension mandrel comprising two half-mandrels into one or more bearing bores and the fracture separation force for separating the bearing cap from the thrust block is produced by spreading the two half-mandrels apart in a force-actuated manner.
This spreading-apart process is usually brought about by mechanically or hydraulically driving a separating wedge (cf. for example U.S. Pat. No. 4,684,267 or FIG. 1 of DE 44 13 255) or by positioning a hydraulically impacted expander between the half-mandrels. In addition, expanders in the form of knuckle joint assemblies are used (cf. for example DE 199 18 067).
It is also known to clamp the thrust block securely to a stationary support and to “sever” the bearing cap in a controlled manner by introducing a tensile force (cf. FIG. 2 of DE 44 13 255). For this purpose, a tie-rod half is placed within the bearing bore in the area of the bearing cap and this half-tie rod is attached, at both sides of the bearing cap, to tensioning tabs which are connected to a hydraulic pulling means that produces the tensile force needed to “sever” the bearing cap.
As a rule, breaking or fracture separation entails the problem of so-called bending strain. Such deformation phenomena are due to the fact that, during the breaking separation process, the fracture cannot be realized absolutely synchronously across the entire breaking separation face. On the contrary, the fracture begins at a point on the breaking separation face and propagates across the entire breaking separation face with a time delay (in the millisecond range). The already detached part bends up with respect to the part not yet separated, thus causing the breaking separation faces to be no longer fitted precisely together after the fracture has occurred. This effect arises particularly noticeably whenever bearing bores or bearing sleeves, the breaking separation face of which is formed by two spaced-apart surface portions, undergo fracture separation. Workpieces that exhibit these deformation phenomena do not comply with quality-related demands specified in bearing or engine construction and are consequently useless.
The prior art counters this type of bending strain in that the parts to be separated are flexibly pressed together at a specific pre-tension. This pre-tension must, however, be overcome during the breaking separation process, because it counteracts the force of fracture separation. To reduce bending strain to an economically viable degree whenever bearing assemblies undergo fracture separation, it will be necessary in practice to operate at relatively high pre-tensions and consequently with very high fracture-separation forces, too.